1. INVESTMENT ANALYSIS & PORTFOLIO MANAGEMENT
Lecture # 30
Dr.Shahid A. Zia

2. Measuring Bond Price Volatility: Duration
Important considerations:
A measure is needed that accounts for both size and timing of cash flows.
Maturity is an inadequate measure of volatility.
It May not have an identical economic lifetime.

3. What is Duration
It is a measure of a bond’s lifetime, stated in years, that accounts for the entire pattern (both size and timing) of the cash flows over the life of the bond.
The weighted average maturity of a bond’s cash flows.
Weights determined by present value of cash flows.

4. Duration A measure of the effective maturity of a bond.
Since the measurement of duration considers the timing and value of intermediate payments.
It is an accurate measure of average life and is more meaningful that maturity for any bond that has coupon payments.
Duration is shorter than maturity for all bonds except zero coupon bonds.
Duration is equal to maturity for zero coupon bonds.

5. Why is Duration Important?
It allows comparison of effective lives of bonds that differ in maturity, coupon.
It is used in bond management strategies particularly immunization.
It Measures bond price sensitivity to interest rate movements, which is very important in any bond analysis.

6. Duration/Price Relationship
Price change is proportional to duration and not to maturity.
One of the key properties of duration is related to price changes.
The concept of modified duration is used extensively in industry.
Duration incorporates both the coupon rate and maturity effects into a single measure.

7. Duration
Duration is an average signifying the point in time when the PV of a security is repaid.
It is a measure of the price sensitivity of a security to interest rate changes. 46 55

8. Duration Is a measure of the effective maturity of a bond.
It is the weighted average of the times until each payment is received, with the weights proportional to the present value of the payment.
Duration is shorter than maturity for all bonds except zero coupon bonds.
Duration is equal to maturity for zero coupon bonds.

9. Uses of Duration
Duration is a measure of interest rate risk that considers the effects of both the coupon rate & maturity changes in bond prices.
By matching the duration of their firm’s assets & liabilities, managers of financial institutions can minimize exposure to interest rate risk.
Duration is the figure that we need to look at when we talking about being able to measure interest rate risk and by looking at the duration will be able to avoid the effect of interest rate risk on our realized rates of return.
Fin 101-Dr. Elinda Fishman Kiss 33 51 42

10. Uses of Duration
Immunization of interest rate risk is a tool that can be used for passive management.
Financial institutions use immunization concept to manage assets and liabilities.
To control for interest rate risk, managers of financial institutions balance the durations of their asset and liability portfolios.
Target date immunization can be used to lock in a fixed rate of return for some investment horizon.

11. Duration problem
Example: $100 par, 6 % coupon, 5 years (10 semi-annual payments of 3% each six months) in an 8 % market ( 4 % semi-annual yield).

12. Duration problem Per (n) CF DF PV of CF nx PV of CF 1 $ 3.0 .9615
2.8845 2
3.0
.9246
2.7738
5.5476 3
.8890
2.667
8.001 4
.8548
2.5664 5
.8219
2.4657
………… 10
103.0
.6756

13. Per (n) CF DF
PV of CF
nx PV of CF 1 3
0.9615
2.8845 2
0.9246
2.7738
5.5476
0.889
2.667
8.001 4
0.8548
2.5644 5
0.8219
2.4657 6
0.7903
2.3709 7
0.7599
2.2797 8
0.7307
2.1921 9
0.7026
2.1078 10
103
0.6756
Sum PV & weighted PV column

14. Duration problem
Duration of this security = / = half years
= years
So the five year 6% coupon security has a duration of 4.36 years in a market where expected yield to maturity = 8%
Find duration if i = 4 %
Is it the same as when i = 8 % ? (hint: no!)
Modified duration = duration / (1 + i ) 45 54

15. Rules for Duration
Rule 1: The duration of a zero-coupon bond equals its time to maturity.
Rule 2: Holding maturity constant, a bond’s duration is higher when the coupon rate is lower.
Rule 3: Holding the coupon rate constant, a bond’s duration generally increases with its time to maturity.
Rule 4: Holding other factors constant, the duration of a coupon bond is higher when the bond’s yield to maturity is lower.

16. Duration Conclusions
To obtain maximum price volatility, investors should choose bonds with the longest duration.
Duration is additive.
Portfolio duration is just a weighted average.
Duration measures volatility which isn’t the only aspect of risk in bonds.
Default risk in bonds.
Interest rate risks in bonds.

17. Convexity
Convexity is very important consideration in the bond market.
Significance of convexity.

18. Convexity
Refers to the degree to which duration changes as the yield to maturity changes.
Price-yield relationship is convex
Duration equation assumes a linear relationship between price and yield.
Convexity largest for low coupon, long-maturity bonds, and low yield to maturity.

19. Pricing Error from Convexity
Price
Pricing Error from
Convexity
11-10 displays the concept of convexity by looking at the duration and the error from the duration line that results from convexity. The hatched area represents pricing error that would result from using the duration concept. The error is larger for large changes in interest rate. T presents the correction for convexity that is used with the pricing relationship.
Duration
Yield

20. Bond price volatility
Bond prices are inversely related to bond yields.
The price volatility of a long-term bond is greater than that of a short-term bond, holding the coupon rate constant.
The price volatility of a low-coupon bond is greater than that of a high-coupon bond, holding maturity constant. 36 45

21. Example of Bond volatility
The price of a 2-year bond (with one year remaining - so really a 1-year bond) fell by 9.57% when market yield increased from 5 % to 6% and rose by 9.71% when market yields fell from 5% to 4%.
This measure of percentage price change is called bond volatility.
What if we had a bond with 30 years remaining & a 5% coupon and market rates rose to 6%.
Again assume semi-annual coupons of 2.5% when market semi-annual yields are 3%.

22. Bond volatility
P = 25/(1.03) + 25/(1.03) /(1.03) /(1.03) /(1.03) /(1.03) /(1.03)30 = =
What is the percentage change in price?
% P = ( )/1000 = - 98/1000 = %
For the same change change in yield (from 5% to 6%) the 1-year security had a 9.57% change in price & the 30-year security had a 13.8% change in price.

23. Bond price volatility
Bond price volatility is the percentage change in bond price for a given change in yield.
Volatility increases with maturity.
A 1% increase in market yields from 5% gives volatility of;
1 year % (price fell to )
15 year - 9.8% (price fell to 902)
30 year % (price fell to )

24. Bond price volatility

25. Zero Coupon
What is the volatility of a 30-year zero coupon bond if market rates change from 5% to 6%
P0 = 1000/ (1.05)30 =
P1 = 1000/ (1.06)30 =
% P = ( )/ = %
Conclusion: lower coupon has more volatility
( % vs % for 5% coupon)

26. Zero Coupon
If assume 60-semi annual compounding periods with c = I = 2.5%, P0 = 1000/ (1.025)60 =
or P1 = 1000/ (1.03)60 =
% P = ( )/ = %

27. Summary Bond prices are inversely related to bond yields.
The price volatility of a longer-maturity security is larger than that of a shorter maturity security, holding the coupon rate constant.
The price volatility of a low coupon security is larger than that of a high coupon security, holding maturity constant.
IRR (Interest rate risk) occurs when realized return doesn’t = YTM
Why does this happen? How can it be avoided?

28. What does the price volatility of a bond depend on?
1. Maturity
2. Coupon
3. Yield to maturity

29. Approximate % change in price of bond
To get a approximate % change in the price of a bond for a change in yield we just multiply it by the change in yield.
This is a linear approximation; good for small change in interest rates.